Enzyme-Linked ImmunoSorbent Assay (“ELISA”) is a biochemical technique commonly used as a medical diagnostic tool to detect the presence of an antibody or an antigen in a sample. During an ELISA test, a sample containing an analyte is subjected to a biochemical process taking place within an individual microwell of a multi-well plate (also known as a “microtiter plate”), for example a standard 96-well plate has an 8×12 array of individual microwells. Depending on the particular test being conducted, a predetermined capture antibody or bio-molecule may be immobilized on the bottom surface of each microwell, and controlled amounts of various fluids (e.g. blocking solution, washing solution, test sample, detection antibody, primary and secondary antibodies, and substrate) may be added to the microwell according to a predetermined protocol that may include periods of controlled incubation and washes. The result of the biochemical process may be viewed using an optical detector measuring absorbance, fluorescence, and/or luminescence, or other properties, to provide a qualitative and/or quantitative test result.
In traditional ELISA testing, all of the wells in a standard 96-well plate are tested for the same analyte, and a single ELISA protocol is used for the entire plate. This standard ELISA has been extended into a profile screen for a panel of analytes in special cases where in each 8 well strip of a plate has a specific analyte. Consequently, if it is necessary to test for more than one analyte, traditional ELISA is costly with respect to sample volume, reagents, and total throughput time.
Newer multiplexed immuno-assay formats provide a multiplexed platform (known as a microarray) containing individual spots of different antigens or capture antibodies on a single microwell bottom. Alternatively, a multiplexed immuno-assay may comprise magnetic bar-coded particles on which specific analyte molecules are immobilized whereby samples may be tested simultaneously for multiple analytes. Each particle is uniquely identified by the barcode. As such, a plurality of bar-coded particles may be provided in each microwell.
A variety of prepared well plates and well strips (a linear strip of wells inserted into a well plate) are commercially available in either standard singleplex or multiplex formats, and specific reagent kits are also commercially available for performing different ELISA/immuno-assay protocols.
Heretofore, automated diagnostic workstations have been designed to perform either standard (singleplex) ELISA testing or multiplex immuno-assay testing, but not both. The standard ELISA workstations are widely used in clinical as well as research settings, whereas higher-priced microarray or magnetic bar-coded particle processing and scanning workstations tend to be found mainly in research settings. Because prior art workstations cannot combine a standard singleplex ELISA based on colorimetry/absorbance with multiplex immuno-assay formats, all the microwells in commercially available well plates are configured either for standard singleplex ELISA or multiplex immuno-assays. Both standard and multiplex wells are not found in the same microtiter plate.
Also, information about loaded well plates and reagent kits may need to be manually programmed into such workstations by an operator to permit full automation of the associated protocol, which can lead to human error.